Many different mechanisms have been employed over the years for securing the vertical legs of a tilt ladder to a tilt drum. In venetian blinds two or more cord ladders extend from a headrail to a bottom rail of a venetian blind. Such ladders include cross-pieces or rungs which support the blind slats horizontally and, when the blind slats are to be tilted, move each slat simultaneously to tilt the array of slats to a desired angularity. The vertical ladder legs, normally in the form of cords, are connected to a rotary drum typically nested in a cradle, both mounted in the blind headrail. The drum is actuated by movement of a tilt wand extending from the headrail and normally hand-rotatable by a user. Rotary motion is transmitted to the drum by means of a tilt rod connected to a gearing assembly, which is in turn connected to thetilt wand. As the drum revolves on its longitudinal axis, the two vertical legs of the ladder raise and lower, providing the means for tilting the slats.
Early designs used a nominally 2.5-5.0 cm wide flexible ladder tape for the vertical legs with about 1 cm horizontal cross-pieces supporting each slat, the cross-pieces being sealed and held between two vertical tape layers. The tops of the two vertical tapes were attached to pairs of foldable tangs on a sheet metal drum of about the same width as the tape and a tape end stapled to the folded tangs to form a closed end loop. Rotation of the drum over about 120.degree. in each direction from the slats horizontal position open and close the blind slats.
In subsequent prior art devices a smaller drum was employed having a single bendable tang forming an essentially closed loop. The top ends of vertical ladder cords are threaded through the closed loop and the distal ends of the cords clamped by suitable staples to inboard portions of the vertical ladder cords forming a cord loop within the drum tang loop. Other manufacturers have used a construction including a brass sleeve crimped around the distal ends of each vertical ladder portion, the sleeves being then directly passed into opposed small holes on the side of the drum and the relatively longer sleeves oriented to be essentially parallel to the longitudinal axis of the drum, or by crossing the ladder legs and running them to holes on opposite sides of the drum so as to hold the ladder depending therefrom.
Plastic rotatable drums have been employed having longitudinal sleeves into which a metal sleeve crimped on the vertical ladder end is inserted. A top entry slit has been included in the plastic sleeves to aid in locking the ladder and metal sleeve into each drum sleeve. An improvement to this general type of construction is seen in the related application where sleeved ends of a ladder cord are inserted into integral sleeves extending from a tilt drum. Another type of ladder-to-drum connection is described in a U.S. patent application now U.S. Pat. No. 4,495,971 of S. Smederod and K. Caysson of S. Ivarson, Sweden, which employs small bullet-like plastic members which have a sharp point which pierces through a vertical ladder portion. The member and ladder end is then jammed into a drum sleeve for holding the ladder end therein. As can be seen each of the above constructions employ separate staples, sleeves or bullets which are affixed to the ladder top distal ends and then that assembly is attached to the drum in various fashions. The use of staples, sleeves and bullets add additional elements to the assembly and increase the cost of manufacture and assembly.